Low structure carbon black and method of making same

ABSTRACT

A carbon black having an I 2  number from 30 mg/g to 200 mg/g and a DBP from 20 cc/100 g to 40 cc/100 g.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/148,870, filed Apr. 23, 2008, which claims priority to U.S.Provisional Applications Nos. 60/926,003, filed Apr. 24, 2007, and60/963,815, filed Aug. 7, 2007, the contents of each which are herebyincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to low structure carbon blacks and methodsof producing them.

2. Description of the Related Art

Carbon blacks are used as pigments in a wide variety of media,including, for example, toners, inkjet inks, and inkjetable colorfilters. The structure and surface area of these blacks are chosen topermit a particular loading level of carbon black in a matrix and toreduce conductivity and charge accumulation in the media. Increasedloading level increases the optical density (OD), a measure of theopacity of a material, of the media but also increases the viscosity ofthe coating compositions used to produce the media. Decreasing thestructure of the component carbon black can decrease viscosity, allowingthinner layers of the media to be deposited without defects, or it canallow more carbon black to be incorporated at a given viscosity,resulting in a higher optical density.

One method of controlling the structure of a furnace carbon black is byadding alkali ions to a furnace while burning a carbonaceous feedstock.For example, in U.S. Pat. No. 5,456,750, increasing the addition ofpotassium to a carbon black furnace decreased the structure of theresulting black. However, the resulting metal component in the carbonblack can contribute to increased conductivity, and non-carbon materialsin the media do not contribute to optical density. In addition, whileoptical density or tint may be increased by increasing surface area, itbecomes increasingly difficult to decrease the structure as the surfacearea is increased. For example, in the '750 patent, those carbon blackshaving the lowest DBP (dibutyl phthalate absorption) also had relativelylower tint than carbon blacks with DBP greater than 40. The lower tintmeans that greater concentrations of the carbon black in a particularmedia would have been required to obtain a desired optical density,increasing the cost of the media and increasing manufacturingdifficulty, since higher concentrations of carbon black are often moredifficult to disperse. Furthermore, as potassium and other metalelements are added to the furnace, the resulting black has more chargedgroups on the surface and is thus more acidic and hydrophilic. Morehydrophilic or acidic blacks (e.g., pH less than 6) may not becompatible with as wide a range of polymers and other components thatwould be otherwise desirable for use in coating or printingapplications. Thus, it is desirable to identify a method of producingcarbon blacks having low structure but also having low amounts of alkalimetals and low acidity and hydrophilicity and that do not compromiseoptical density and viscosity in coating, toner, or ink compositionsincorporating the carbon black.

SUMMARY OF THE INVENTION

In one aspect, the invention includes a carbon black having an iodinenumber (I₂ number) from 30 to 200 mg/g, a DBP from 20 cc/100 g to 40cc/100 g, and a total concentration of Group IA and HA elements, inμg/g, of at most y+(15*I₂ number), wherein y is 250, 100, −50, −150, or−350. For example, the carbon black may have a DBP of from 20 to 40cc/100 g, from 20 to 30 cc/100 g, from 30 to 39 cc/100 g, or a DBP inany range bounded by any of these endpoints. Alternatively or inaddition, the carbon black may have an iodine number of from 30 to 200mg/g, from 30 to 45 mg/g, from 45 to 100 mg/g, from 70 to 100 mg/g, from100 to 150 mg/g, from 150 to 200 mg/g, 70 to 200 mg/g, or in any rangebounded by any of these endpoints. The carbon black may be characterizedby at least one of the following: an M-ratio from 1 to less than 1.25; apH from 6 to 10; a water spreading pressure of at most 6 mJ/m²; or atint obeying the equation tint=x+0.44*I₂ number, where x is from 45 to90, for example, from 60 to 90 or from 75 to 90. The carbon black may bean oxidized carbon black, a heat treated carbon black, or a modifiedcarbon black comprising an attached organic group.

In another aspect, the invention includes a carbon black having an I₂number from 30 to 200 mg/g, a DBP from 20 cc/100 g to 40 cc/100 g, andan M-ratio from 1.00 to less than 1.25. For example, the carbon blackmay have a DBP of from 20 to 40 cc/100 g, from 20 to 30 cc/100 g, from30 to 39 cc/100 g, or a DBP in any range bounded by any of theseendpoints. Alternatively or in addition, the carbon black may have aniodine number of from 30 to 200 mg/g, from 30 to 45 mg/g, from 45 to 100mg/g, from 70 to 100 mg/g, from 100 to 150 mg/g, from 150 to 200 mg/g,70 to 200 mg/g, or in any range bounded by any of these endpoints. Thecarbon black may be characterized by at least one of the following: a pHfrom 6 to 10; a total concentration of Group IA and IIA elements, inμg/g, of at most y+(15*I₂ number), wherein y is 250, 100, −50, −150, or−350; a water spreading pressure of at most 6 mJ/m²; or a tint obeyingthe equation tint=x+0.44*I₂ number, where x is from 45 to 90, forexample, from 60 to 90 or from 75 to 90. The carbon black may be anoxidized carbon black, a heat treated carbon black, or a modified carbonblack comprising an attached organic group.

In another aspect, the invention includes a carbon black having an I₂number from 30 to 200 mg/g, a DBP from 20 cc/100 g to 40 cc/100 g, awater spreading pressure of at most 6 mJ/m², and an M-ratio from 1.00 toless than 1.25. For example, the carbon black may have a DBP of from 20to 40 cc/100 g, from 20 to 30 cc/100 g, from 30 to 39 cc/100 g, or a DBPin any range bounded by any of these endpoints. Alternatively or inaddition, the carbon black may have an iodine number of from 30 to 200mg/g, from 30 to 45 mg/g, from 45 to 100 mg/g, from 70 to 100 mg/g, from100 to 150 mg/g, from 150 to 200 mg/g, 70 to 200 mg/g, or in any rangebounded by any of these endpoints. The carbon black may be characterizedby at least one of the following: a pH from 6 to 10; a totalconcentration of Group IA and IIA elements, in μg/g, of at most y+(15*I₂number), wherein y is 250, 100, −50, −150, or −350; or a tint obeyingthe equation tint=x+0.44*I₂ number, where x is from 45 to 90, forexample, from 60 to 90 or from 75 to 90. The carbon black may be anoxidized carbon black, a heat treated carbon black, or a modified carbonblack comprising an attached organic group.

In another aspect, the invention includes a carbon black having an I₂number from 70 to 200 mg/g, a DBP from 20 cc/100 g to 50 cc/100 g, and awater spreading pressure of at most 6 mJ/m². For example, the carbonblack may have a DBP value of from 20 to 40 cc/100 g, from 20 to 50cc/100 g, 20 to 45 cc/100 g, from 20 to 30 cc/100 g, from 30 to 39cc/100 g, from 30 to 45 cc/100 g, from 40 to 45 cc/100 g, from 45 to 50cc/100 g, or a DBP in any range bounded by any of these endpoints.Alternatively or in addition, the carbon black may have an iodine numberof from 70 to 100 mg/g, from 100 to 150 mg/g, from 150 to 200 mg/g, 70to 200 mg/g, or in any range bounded by any of these endpoints. Thecarbon black may be characterized by at least one of the following: anM-ratio from 1 to less than 1.25; a pH from 6 to 10; a totalconcentration of Group IA and IIA elements, in μg/g, of at most y+(15*I₂number), wherein y is 250, 100, −50, −150, or −350; or a tint obeyingthe equation tint=x+0.44*I₂ number, where x is from 45 to 90, forexample, from 60 to 90 or from 75 to 90. The carbon black may be anoxidized carbon black, a heat treated carbon black, or a modified carbonblack comprising an attached organic group.

In another aspect, the invention includes a process for producing acarbon black product having an iodine number from 30 mg/g to 200 mg/gand a DBP from 20 cc/100 g to 40 cc/100 g. For example, the carbon blackmay have a DBP of from 20 to 40 cc/100 g, from 20 to 30 cc/100 g, from30 to 39 cc/100 g, or a DBP in any range bounded by any of theseendpoints. Alternatively or in addition, the carbon black may have aniodine number of from 30 to 200 mg/g, from 30 to 45 mg/g, from 45 to 100mg/g, from 70 to 100 mg/g, from 100 to 150 mg/g, from 150 to 200 mg/g,70 to 200 mg/g, or in any range bounded by any of these endpoints. Themethod includes forming a stream of combustion gases by reacting apreheated air stream with a fuel, introducing feedstock into the streamof combustion gases at a predetermined number of points in an axialplane to form an effluent and start pyrolysis of the feedstock in theeffluent, introducing an auxiliary hydrocarbon into the stream ofcombustion gases at the predetermined number of points in an axialplane, wherein the points of injection of the feedstock and theauxiliary hydrocarbon alternate in the axial plane, additionallyintroducing into the stream of combustion gases at least one substancecontaining at least one Group IA or Group IIA element or a combinationthereof, and quenching the pyrolysis using water that has been subjectedto reverse osmosis treatment, wherein the total of Group IA and IIAelements, in μg/g, in the carbon black product is at most y+15*I₂number, wherein y is 250, 100, −50, −150, or −350. The overallcombustion ratio may be greater than 26%. The predetermined number maybe three. The auxiliary hydrocarbon may hydrocarbonaceous and may beintroduced in an amount such that the carbon content of the auxiliaryhydrocarbon is at most about 20% by weight of the total carbon contentof all fuel streams injected into the reactor. The auxiliary hydrocarbonmay be in gaseous form. The carbon black may be characterized by atleast one of the following: an M-ratio from 1 to less than 1.25; a pHfrom 6 to 10; a water spreading pressure of at most 6 mJ/m²; or a tintobeying the equation tint=x+0.44*I₂ number, where x is from 45 to 90,for example, from 60 to 90 or from 75 to 90. The process may furtherinclude modifying a surface chemistry or a microstructure of the carbonblack. The process may further include modifying the carbon black toattach an organic group, oxidizing the carbon black, or heat treatingthe carbon black.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are intended to provide further explanation of the presentinvention, as claimed.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described with reference to the several figures of thedrawing, in which,

FIG. 1 is a cross-sectional view of a portion of one type of furnacecarbon black reactor that may be utilized to produce carbon blacks foruse in exemplary embodiments of the invention.

FIG. 2 is a sample histogram of the weight fraction of the aggregates ofa carbon black sample versus the Stokes Diameter in a given sample.

FIG. 3 is a graph showing the viscosity of millbases produced using acarbon black according to an exemplary embodiment of the invention and acommercially available carbon black.

DETAILED DESCRIPTION OF THE INVENTION

We have found that carbon blacks with low structure, e.g., a DBP of 20cc/100 g to 40 or 50 cc/100 g, can be obtained at intermediate to highsurface area, e.g., an iodine number of 30 mg/g or 70 mg/g to 200 mg/g,by a combination of adding alkali and/or alkaline earth salts to thefeedstock of a carbon black furnace operated under particularconditions, for example, with addition of auxiliary hydrocarbon and anincreased overall combustion ratio, as described in more detail below.The resulting carbon black has neutral to moderately basic pH and isalso more hydrophobic than would have been expected from the reactionconditions employed. The levels of structure are significantly lowerthan what could be achieved through the use of alkali or alkaline earthaddition or auxiliary hydrocarbon alone. Furthermore, the amount ofalkali or alkaline earth metals in the carbon black is lower than whatis usually found for lower structure carbon blacks with intermediate tohigh surface area, e.g., iodine number of 30 to 200 m²/g. Despite thelow structure, the carbon blacks have relatively high tint. In addition,the carbon blacks exhibit a lower M-ratio than prior art blacks havingsimilar surface areas or structures.

In one embodiment, a carbon black has a DBP from 20 cc/100 g to 40cc/100 g and an I₂ number from 30 to 200 mg/g. For example, the carbonblack may have a DBP of from 20 to 40 cc/100 g, from 20 to 30 cc/100 g,from 30 to 39 cc/100 g, or a DBP in any range bounded by any of theseendpoints. Alternatively or in addition, the carbon black may have aniodine number of from 30 to 200 mg/g, from 30 to 45 mg/g, from 45 to 100mg/g, from 70 to 100 mg/g, from 100 to 150 mg/g, from 150 to 200 mg/g,70 to 200 mg/g, or in any range bounded by any of these endpoints. Asknown to those skilled in the art, at fixed porosity, increased surfacearea correlates with smaller primary particle size.

In an alternative embodiment, the carbon black may have a DBP less than50 cc/100 g and an iodine number of from 70 to 200 mg/g. For example,the carbon black may have a DBP value of from 20 to 40 cc/100 g, from 20to 50 cc/100 g, 20 to 45 cc/100 g, from 20 to 30 cc/100 g, from 30 to 39cc/100 g, from 30 to 45 cc/100 g, from 40 to 45 cc/100 g, from 45 to 50cc/100 g, or a DBP in any range bounded by any of these endpoints.Alternatively or in addition, the carbon black may have an iodine numberof from 70 to 100 mg/g, from 100 to 150 mg/g, from 150 to 200 mg/g, 70to 200 mg/g, or in any range bounded by any of these endpoints.

In any of the embodiments described herein, the carbon black primaryparticles may approach an essentially overall spherical geometry.

The carbon black may additionally have one or more of the followingproperties, each of which is discussed in more detail below. The totalconcentration of alkali and alkaline earth elements (e.g., Group IA andIIA elements) in μg/g, may be at most (y+15*I₂ number), where y is 250,100, −50, −150, or −350. The M-ratio, the ratio of the median Stokesdiameter to the mode of the Stokes diameter of a carbon black sample,may be from 1.0 to less than 1.25, for example, between 1.22 and 1.24 orin any range defined by any of these endpoints. The tint of the carbonblack may be defined by the following equation:Tint=x+0.44*I ₂ numberwhere x may be from 45 to 90, for example, from 60 to 90 or from 75 to90. The carbon black may have a pH from 6 to 10, for example, from 6 to8, from 8 to 10, from 7 to 9, or in any range defined by any of theseendpoints. The water spreading pressure (WSP), a measure of theinteraction energy between the carbon black surface and water vapor, maybe at most 6 mJ/m², for example, at most 5 mJ/m², at most 4 mJ/m², from2 to 6 mJ/m², from 2 to 5 mJ/m² from 3 to 6 mJ/m², from 3 to 5 mJ/m², orin any range defined by any of the endpoints herein.

We have identified operating conditions that permit low structure carbonblacks to be produced with high surface areas but with lower amounts ofGroup IA and Group IIA metal elements than have been previously used,thereby reducing the amount of these metals in the carbon black product.In general, for a carbon black having a given surface area, thestructure can only be depressed to a certain amount by addition of metalelements, after which additional metal element addition does not furtherinfluence structure. However, we have produced carbon blacks havingsignificantly lower structure, e.g., a dibutylphthalate absorption (DBP)value of 20 cc/100 g to 40 cc/100 g or 20 cc/100 g to 50 cc/100 g, thanhas been previously achievable for intermediate surface area blacks, notto mention high surface area blacks. Exemplary apparatus and reactionconditions are described below and in the Examples. Carbon blacksaccording to various embodiments of the invention may also be producedusing a variety of other apparatus, including those described in, forexample, U.S. Pat. Nos. 5,456,750, 4,391,789; 4,636,375; 6,096,284; and5,262,146. One of skill in the art will recognize how to adapt thereaction conditions described below to produce carbon blacks accordingto the various embodiments of the invention in other apparatus.

In one embodiment, carbon blacks are produced in a modular furnacecarbon black reactor 2, such as that depicted in FIG. 1, having acombustion zone 10, which has a zone of converging diameter 11,transition zone 12, entry section 18, and reaction zone 19. The diameterof the combustion zone 10, up to the point where the zone of convergingdiameter 11 begins, is shown as D-1; the diameter of zone 12, as D-2;the diameters of the stepped entry section, 18, as D-4, D-5, D-6, andD-7; and the diameter of zone 19, as D-3. The length of the combustionzone 10, up to the point where the zone of converging diameter 11begins, is shown as L-1; the length of the zone of converging diameteris shown as L-2; the length of the transition zone is shown as L-3; andthe lengths of the steps in the reactor entry section, 18, as L-4, L-5,L-6 and L-7.

To produce carbon blacks, hot combustion gases are generated incombustion zone 10 by contacting a liquid or gaseous fuel with asuitable oxidant stream such as air, oxygen, mixtures of air and oxygenor the like. Among the fuels suitable for use in contacting the oxidantstream in combustion zone 10 to generate the hot combustion gases areany of the readily combustible gas, vapor, or liquid streams such asnatural gas, hydrogen, carbon monoxide, methane, acetylene, alcohol, orkerosene. It is generally preferred, however, to utilize fuels having ahigh content of carbon-containing components and in particular,hydrocarbons. The volumetric ratio of air to natural gas utilized toproduce the carbon blacks of the present invention may preferably befrom about 10:1 to about 100:1. To facilitate the generation of hotcombustion gases, the oxidant stream may be preheated. In someembodiments, the overall combustion ratio is at least 26%, for example,from 26% to 35%, from 28% to 35%, from 30% to 35%, at least 28%, or atleast 30%.

The hot combustion gas stream flows downstream from zones 10 and 11 intozones 12, 18, and 19. The direction of the flow of hot combustion gasesis shown in the figure by the arrow. Carbon black-yielding feedstock 30is introduced at point 32 (located in zone 12), and/or at point 70(located in zone 11). Suitable for use herein as carbon black-yieldinghydrocarbon feedstocks, which are readily volatilizable under theconditions of the reaction, are unsaturated hydrocarbons such asacetylene; olefins such as ethylene, propylene, butylene; aromatics suchas benzene, toluene and xylene; certain saturated hydrocarbons; andother hydrocarbons such as kerosenes, naphthalenes, terpenes, ethylenetars, aromatic cycle stocks and the like.

The distance from the end of the zone of converging diameter 11 to point32 is shown as F-1. Generally, carbon black-yielding feedstock 30 isinjected in the form of a plurality of streams which penetrate into theinterior regions of the hot combustion gas stream to insure a high rateof mixing and shearing of the carbon black-yielding feedstock by the hotcombustion gases so as to rapidly and completely decompose and convertthe feedstock to carbon black.

Auxiliary hydrocarbon is introduced at point 70 through probe 72 orthrough auxiliary hydrocarbon passages 75 in the walls which form theboundaries of zone 12 of the carbon black forming process or throughauxiliary hydrocarbon passages 76 in the walls which form the boundariesof zones 18 and/or 19 of the carbon black forming process. The term“auxiliary hydrocarbon” as used herein refers to hydrogen or anyhydrocarbon having a molar hydrogen-to-carbon ratio greater than themolar hydrogen-to-carbon ratio of the feedstock and may be gaseous orliquid. Exemplary hydrocarbons include but are not limited to thosematerials described herein as suitable for use as fuels and/orfeedstocks. In certain embodiments of the invention, the auxiliaryhydrocarbon is natural gas. The auxiliary hydrocarbon may be introducedat any location between the point immediately after the initialcombustion reaction of the first-stage fuel and the point immediatelybefore the end of formation of carbon black provided that unreactedauxiliary hydrocarbon eventually enters the reaction zone. In certainpreferred embodiments, the auxiliary hydrocarbon is introduced in thesame axial plane as the feedstock. In the Examples described below, theauxiliary hydrocarbon was introduced through three orifices in the sameaxial plane as the carbon black yielding feedstock streams. The orificesare preferably arranged in an alternating pattern, one feedstock, thenext auxiliary hydrocarbon, etc., spaced evenly around the outerperiphery of section 12. The quantity of auxiliary hydrocarbon added tothe reactor may be adjusted so that carbon content of the auxiliaryhydrocarbon is at most about 20% by weight of the total carbon contentof all fuel streams injected into the reactor, for example, from about 1to about 5%, from about 5% to about 10%, from about 10% to about 15%,from about 15% to about 20%, or in any range bounded by any of theseendpoints. In certain preferred embodiments, the carbon content of theauxiliary hydrocarbon is from about 3% to about 6% by weight of thetotal carbon content of all fuel streams injected into the reactor.

The distance from point 32 to point 70 is shown as H-1.

In some embodiments, specific alkali or alkaline earth materials areadded to the carbon black as a structure modifier in such an amount thatthe total concentration in the resulting carbon black of alkali oralkaline earth materials is low. Preferably, the substance contains atleast one alkali metal or alkaline earth metal. In certain exemplaryembodiments, potassium ion is added to the feedstock and eventuallyincorporated into the carbon black, while the total Group IA and HAelement concentration remains low. Other examples of Group IA and IIAelements that may be exploited for use in various embodiments includelithium, sodium, potassium, rubidium, cesium, francium, calcium, barium,strontium, or radium, or any combination of two or more of these. Thesubstance can be a solid, solution, dispersion, gas, or any combinationthereof. More than one substance having the same or different Group IAor Group IIA element can be used. If multiple substances are used, thesubstances can be added together, separately, sequentially, or indifferent reaction locations. For purposes of the present invention, thesubstance can be the metal (or metal ion) itself, a compound containingone or more of these elements, including a salt containing one or moreof these elements, and the like. Exemplary salts include both organicand inorganic salts, for example, salts, e.g., of sodium and/orpotassium, with any of chloride, acetate, or formate, or combinations oftwo or more such salts. Preferably, the substance is capable ofintroducing a metal or metal ion into the reaction that is ongoing toform the carbon black product. For instance, the substance can be addedat any point prior to the complete quenching, including prior to theintroduction of the carbon black yielding feedstock in the first stage;during the introduction of the carbon black yielding feedstock in thefirst stage; after the introduction of the carbon black yieldingfeedstock in the first stage; prior to, during, or immediately after theintroduction of the auxiliary hydrocarbon; or any step prior to completequenching. More than one point of introduction of the substance can beused. The amount of the metal-containing substance can be any amount aslong as a carbon black product can be formed. As described above, theamount of the substance can be added in an amount such that the totalamount of Group IA and/or Group IIA elements (i.e., the totalconcentration of Group IA and Group IIA elements contained the carbonblack) in μg/g is at mosty+15*I ₂ numberwhere y may be 250, 100, −50, −200, or −350. In certain embodiments, thesubstance introduces a Group IA element; for example, the substance mayintroduce potassium or potassium ion. The substance can be added in anyfashion including any conventional means. In other words, the substancecan be added in the same manner that a carbon black yielding feedstockis introduced. The substance can be added as a gas, liquid, or solid, orany combination thereof. The substance can be added at one point orseveral points and can be added as a single stream or a plurality ofstreams. The substance can be mixed in with the feedstock, fuel, and/oroxidant prior to and/or during their introduction.

In certain embodiments, the substance containing at least one Group IAor Group IIA element is introduced into the feedstock by incorporationof a salt solution into the feedstock. In certain preferred embodiments,salt solutions are mixed with the feedstock such that the concentrationof all alkali metal and/or alkaline metal ions is from about 0 to about1 weight percent. Upon combustion, the metal ions can becomeincorporated into the carbon black.

The mixture of carbon black-yielding feedstock and hot combustion gasesflows downstream through zone 12 into zone 18 and then into zone 19.Quench 60, located at point 62, injecting quenching fluid 50, which maybe water, is utilized to stop the chemical reaction when carbon blacksare formed. Point 62 may be determined in any manner known to the artfor selecting the position of a quench to stop pyrolysis. One method fordetermining the position of the quench to stop pyrolysis is bydetermining the point at which an acceptable Spectronic 20 value for thecarbon black is reached. Q is the distance from the beginning of zone 18to quench point 62, and will vary according to the position of quench60. In some embodiments, reverse osmosis water is used as the quenchingfluid to minimize the amount of additional metal and other elements thatare added to the carbon black during quenching.

After the mixture of hot combustion gases and carbon black-yieldingfeedstock is quenched, the cooled gases pass downstream into anyconventional cooling and separating means whereby the carbon blacks arerecovered. The separation of the carbon black from the gas stream isreadily accomplished by conventional means such as a precipitator,cyclone separator or bag filter. This separation may be followed bypelletizing using, for example, a wet pelletizer.

In certain embodiments, the carbon blacks may be modified to attach anorganic group to the surface, oxidized, or subjected to heat treatment.Carbon black may be heat treated in an inert atmosphere to increase thegraphite content of the carbon black. One of skill in the art willrecognize that the time and temperature of the heat treatment may beadjusted to achieve a desired amount of graphitization.

Oxidized carbon blacks are oxidized using an oxidizing agent in order tointroduce polar, ionic, and/or ionizable groups onto the surface. Carbonblacks prepared in this way have been found to have a higher degree ofoxygen-containing groups on the surface. Oxidizing agents include, butare not limited to, oxygen gas, ozone, NO₂ (including mixtures of NO₂and air), peroxides such as hydrogen peroxide, persulfates, includingsodium, potassium, or ammonium persulfate, hypohalites such a sodiumhypochlorite, halites, halates, or perhalates (such as sodium chlorite,sodium chlorate, or sodium perchlorate), oxidizing acids such a nitricacid, and transition metal containing oxidants, such as permanganatesalts, osmium tetroxide, chromium oxides, or ceric ammonium nitrate.Mixtures of oxidants may also be used, particularly mixtures of gaseousoxidants such as oxygen and ozone. In addition, carbon blacks preparedusing other surface modification methods to introduce ionic or ionizablegroups onto a pigment surface, such as chlorination and sulfonylation,may also be used.

Modified carbon blacks may be prepared using any method known to thoseskilled in the art such that organic chemical groups are attached to thecarbon black. For example, the modified carbon black can be preparedusing the methods described in U.S. Pat. Nos. 5,554,739, 5,707,432,5,837,045, 5,851,280, 5,885,335, 5,895,522, 5,900,029, 5,922,118, and6,042,643, and PCT Publication WO 99/23174, the descriptions of whichare fully incorporated herein by reference. Such methods provide for amore stable attachment of the groups onto the carbon black compared todispersant type methods, which use, for example, polymers and/orsurfactants. Other methods for preparing the modified carbon blackinclude reacting a carbon black having available functional groups witha reagent comprising the organic group, such as is described in, forexample, U.S. Pat. No. 6,723,783, which is incorporated in its entiretyby reference herein. Such functional carbon black may be prepared usingthe methods described in the references incorporated above. In addition,modified carbon blacks containing attached functional groups may also beprepared by the methods described in U.S. Pat. Nos. 6,831,194 and6,660,075, U.S. Patent Publication Nos. 2003-0101901 and 2001-0036994,Canadian Patent No. 2,351,162, European Patent No. 1 394 221, and PCTPublication No. WO 04/63289, as well as in N. Tsubokawa, Polym. Sci.,17, 417, 1992, each of which is also incorporated in its entirety byreference herein.

In the furnace, the specific iodine number and DBP of the carbon blackare controlled by simultaneously adjusting the burner natural gas rate,feedstock rate, metal salt concentration, and auxiliary hydrocarbon rateand location to achieve the desired properties. The iodine number can beincreased by increasing the burner natural gas rate, decreasing thefeedstock rate, increasing the metal salt concentration, and/ordecreasing the auxiliary hydrocarbon rate. The DBP can be increased byincreasing the burner natural gas rate, increasing or decreasing thefeedstock rate (depending on other factors), decreasing the metal saltconcentration, and/or decreasing the auxiliary hydrocarbon rate. Wherethe auxiliary hydrocarbon is increased e.g., such that it provides morethat 8% or 10% of the total carbon content in the reactor, it may bedesirable to reduce the amount of feedstock in the reactor to maintainor increase the surface area of the resulting carbon black. Under theseconditions, low structure might also be achieved with lower amounts ofalkali or alkaline earth materials. The variables discussed herein alsoaffect other characteristics of the carbon black such as tint, WSP, pH,M-ratio, and residual metal content. The exact levels of each variablerequired to create carbon black with the desired properties depend onthe geometry of the reactor and the method of injection of each speciesinto the reactor. Examples are described in more detail below.

We have unexpectedly found that certain conditions for introducing theauxiliary gas, including a decreased injection orifice diameter,increased feed rate, and injection of the auxiliary gas in the sameaxial plane as the carbon-black yielding feedstock, in combination withspecific concentrations of alkali and/or alkaline earth elements in thefeedstock, as well as specific diameters and lengths for the variouscombustion zones, enabled us to produce carbon blacks having both lowstructure and high surface area. Furthermore, the carbon blacks havestructures that are significantly lower, e.g., 20 cc/100 g to 40 cc/100g or 50 cc/100 g, than what has been previously achievable forintermediate or high surface area blacks, e.g., 30-200 m²/g or 70 to 200m²/g. The amount of alkali or alkaline earth metals in the carbon blackis lower than what is usually found for lower structure carbon blackswith intermediate to high surface area. The resulting carbon black hasthe low DBP that facilitates dispersion and reduces viscosity of mediain which the carbon black is incorporated to ease manufacturing withouta reduction in surface area, which can decrease optical density indevices produced from the carbon black. Furthermore, the low level ofalkali and alkaline earth materials further allows low DBP blacks to beemployed in electronic applications without sacrificing resistivity. Theincreased tint exhibited by these carbon blacks decreases the amount ofcarbon black that must be used in a carrier to achieve a desired opticaldensity.

We have also unexpectedly discovered that use of carbon black having anM-ratio less than 1.25 increases the optical density of materials intowhich the carbon black is incorporated with respect to carbon blackshaving the same structure and surface area but higher M-ratios. Thisallows lesser quantities of carbon black to be used to obtain a givenoptical density, reducing the viscosity of millbases and other fluidmedia containing the carbon black that are used to produce suchmaterials.

Carbon blacks having a neutral pH or slightly basic pH rather than anacidic pH may be more compatible with certain polymers and othermaterials that can be used to produce coatings, inks, toners, and othermedia, expanding the range of compositions that may be combined withcarbon black for these applications. In addition, such carbon blackswill interact differently with the alkaline developers typicallyemployed in the production of black matrix and resist coatings thanacidic carbon blacks and may improve the development characteristics ofresists, black matrices, and other coatings employing alkalinedevelopers.

The lower WSP exhibited by these carbon blacks indicates that they aremore hydrophobic than carbon blacks having similar surface area orstructure but prepared by prior art methods. Carbon blacks with lowwater spreading pressures, e.g., in the range described above, may bemore compatible with certain polymers and other materials that can beused to produce coatings, inks, toners, and other materials, expandingthe range of compositions that may be combined with carbon black forthese applications. In addition, such carbon blacks will interactdifferently with the alkaline developers typically employed in theproduction of black matrix and resist coatings than more hydrophiliccarbon blacks and may improve the development characteristics ofresists, black matrices, and other coatings employing alkalinedevelopers.

Performance of dispersions, coatings, and devices that include carbonblacks will depend on a variety of factors. We have found thatdispersions including a resin and at least one carbon black having a lowlevel of structure, e.g., a DBP of 20 cc/100 g to 40 or 50 cc/100 g, canbe produced with higher loadings of carbon black while maintainingNewtonian flow. Furthermore, such dispersions may be used to producecoatings exhibiting improved electrical and optical properties comparedto coatings comprising the same resin and more highly structured carbonblacks having the same or similar surface areas.

The ability to increase carbon black loading provides other benefits tomaterials such as toners, inks, black matrix, photoresist, and millbasesused to prepare these and other products. As the carbon blackconcentration is increased in such media, properties such as curability,developability, patternability, and adhesion to glass are affected. Inmany cases, one of these properties limits the upper concentration ofcarbon black that is acceptable in the coating, which in turn imposes anupper limit on the achievable optical density of the film. Exploitinglow structure carbon blacks according to certain embodiments of theinvention allows the preparation of films with higher loading of carbonblack while maintaining high resistivity and film smoothness.

The following testing procedures were used in evaluating the analyticaland physical properties of the carbon blacks. Iodine adsorption numberof the carbon blacks (I₂ No.) was determined according to ASTM TestProcedure D-1510-08. Tinting strength (Tint) of the carbon blacks wasdetermined according to ASTM Test Procedure D3265-07. The DBP (dibutylphthalate value) of the carbon blacks was determined according to theprocedure set forth in ASTM D2414-08. Nitrogen surface area and STSAsurface area were measured as per ASTM D6556-07. Ash content wasmeasured as per ASTM D1506-99. The pH was determined by dispersing aknown amount of carbon black in water and measuring the pH of theaqueous phase using a pH probe (ASTM D1512-05). Spectronic 20 wasmeasured as per ASTM D1618-99. Na and K content were measured viainductively coupled plasma (ICP) analysis.

The median and mode Stokes diameters were determined from a histogram ofthe weight fraction of carbon black versus the Stokes diameter of thecarbon black aggregates, as shown in FIG. 2 and described in U.S. Pat.No. 5,456,750. Briefly, the data used to generate the histogram aredetermined by the use of a disk centrifuge such as the one manufacturedby Joyce Loebl Co. Ltd. of Tyne and Wear, United Kingdom.

The following procedure is a modification of the procedure described inthe instruction manual of the Joyce Loebl disk centrifuge file referenceDCF 4.008 published on Feb. 1, 1985, the teachings of which are herebyincorporated by reference, and was used in determining the data. 10 mg(milligrams) of a carbon black sample are weighed in a weighing vessel,then added to 50 cc of a solution of 10% absolute ethanol and 90%distilled water which is made 0.05% NONIDET P-40 surfactant (NONIDETP-40 is a registered trademark for a surfactant manufactured and sold byShell Chemical Co.). The resulting suspension is dispersed by means ofultrasonic energy for 15 minutes using Sonifier Model No. W 385,manufactured and sold by Heat Systems Ultrasonics Inc., Farmingdale,N.Y.

Prior to the disk centrifuge run the following data are entered into thecomputer which records the data from the disk centrifuge:

1. The specific gravity of carbon black, taken as 1.86 g/cc;

2. The volume of the solution of the carbon black dispersed in asolution of water and ethanol, which in this instance is 0.5 cc.;

3. The volume of spin fluid, which in this instance is 10 cc of water;

4. The viscosity of the spin fluid, which in this instance is taken as0.933 centipoise at 23 degrees C.;

5. The density of the spin fluid, which in this instance is 0.9975 g/ccat 23 degrees C.;

6. The disk speed, which in this instance is 8000 rpm;

7. The data sampling interval, which in this instance is 1 second. Thedisk centrifuge is operated at 8000 rpm while the stroboscope isoperating. 10 cc of distilled water are injected into the spinning diskas the spin fluid. The turbidity level is set to 0; and 1 cc of thesolution of 10% absolute ethanol and 90% distilled water is injected asa buffer liquid. The cut and boost buttons of the disk centrifuge arethen operated to produce a smooth concentration gradient between thespin fluid and the buffer liquid and the gradient is monitored visually.When the gradient becomes smooth such that there is no distinguishableboundary between the two fluids, 0.5 cc of the dispersed carbon black inaqueous ethanol solution is injected into the spinning disk and datacollection is started immediately. If streaming occurs the run isaborted. The disk is spun for 20 minutes following the injection of thedispersed carbon black in aqueous ethanol solution. Following the 20minutes of spinning, the disk is stopped, the temperature of the spinfluid is measured, and the average of the temperature of the spin fluidmeasured at the beginning of the run and the temperature of the spinfluid measured at the end of the run is entered into the computer whichrecords the data from the disk centrifuge. The data is analyzedaccording to the standard Stokes equation and is presented using thefollowing definitions:

Carbon black aggregate—a discrete, rigid colloidal entity that is thesmallest dispersible unit; it is composed of extensively coalescedparticles;

Stokes diameter—the diameter of a sphere which sediments in a viscousmedium in a centrifugal or gravitational field according to the Stokesequation. A non-spherical object, such as a carbon black aggregate, mayalso be represented in terms of the Stokes diameter if it is consideredas behaving as a smooth, rigid sphere of the same density, and rate ofsedimentation as the object. The customary units are expressed innanometer diameters.

Mode (Dmode for reporting purposes)—The Stokes diameter at the point ofthe peak (Point A of FIG. 2 herein) of the distribution curve for Stokesdiameter.

Median Stokes diameter— (Dst for reporting purposes) the point on thedistribution curve of Stokes diameter where 50% by weight of the sampleis either larger or smaller. It therefore represents the median value ofthe determination.

The water spreading pressure was measured by observing the mass increaseof a sample as it adsorbs water from a controlled atmosphere. In thetest, the relative humidity (RH) of the atmosphere around the sample isincreased from 0% (pure nitrogen) to ˜100% (water-saturated nitrogen).If the sample and atmosphere are always in equilibrium, the waterspreading pressure (π_(e)) of the sample is defined as:

$\pi_{e} = {\frac{RT}{A}{\int_{o}^{P_{o}}{\Gamma\ {\mathbb{d}\ln}\; P}}}$where R is the gas constant, T is the temperature, A is the nitrogensurface area of the sample, F is the amount of adsorbed water on thesample (converted to moles/gm), P is the partial pressure of water inthe atmosphere, and P_(o) is the saturation vapor pressure in theatmosphere. In practice, the equilibrium adsorption of water on thesurface is measured at one or (preferably) several discrete partialpressures and the integral is estimated by the area under the curve.

The following procedure may be used to measure the water spreadingpressure. Before analysis, 100 mg of the carbon black to be analyzed isdried in an oven at 125° C. for 30 minutes. After ensuring that theincubator in a Surface Measurement Systems DVS1 instrument (supplied bySMS Instruments, Monarch Beach, Calif.) has been stable at 25° C. for 2hours, sample cups are loaded in both the sample and reference chambers.The target RH is set to 0% for 10 minutes to dry the cups and toestablish a stable mass baseline. After discharging static and taringthe balance, approximately 8 mg of carbon black is added to the cup inthe sample chamber. After sealing the sample chamber, the sample isallowed to equilibrate at 0% RH. After equilibration, the initial massof the sample is recorded. The relative humidity of the nitrogenatmosphere is then increased sequentially to levels of approximately 5,10, 20, 30, 40, 50, 60, 70, 78, 87, and 92% RH, with the system allowedto equilibrate for 20 minutes at each RH level. The mass of wateradsorbed at each humidity level is recorded, from which water spreadingpressure is calculated via the above equation.

The present invention will be further clarified by the followingexamples which are intended to be only exemplary in nature

EXAMPLES Example 1

Carbon blacks were prepared in a reactor as described above and shown inFIG. 1 (example C1 is a comparative example), utilizing the reactorconditions and geometry set forth in Table 2. Natural gas was employedas both the fuel for the combustion reaction and the auxiliaryhydrocarbon. An aqueous solution of potassium acetate was used as thealkali metal-containing material, and was mixed with the feedstock priorto injection into the reactor. The reaction was quenched with waterpurified by reverse osmosis. The liquid feedstock had the propertiesindicated in Table 1, below.

TABLE 1 Feedstock Properties Hydrogen/Carbon Ratio 0.91 Hydrogen (wt %)6.97 Carbon (wt %) 91.64 Sulfur (wt %) 0.81 Nitrogen (wt %) 0.35 Oxygen(wt %) 0.23 Specific Gravity at 60° F. [ASTM D-287] 1.1029

TABLE 2 Reactor Geometry and Operating Conditions Example No. A B C D ECl D-1 (m) 0.18 0.18 0.18 0.18 0.18 0.18 D-2 (m) 0.11 0.11 0.11 0.110.11 0.11 D-3 (m) 0.91 0.91 0.91 0.91 0.91 0.91 D-4 (m) 0.91 0.91 0.910.91 0.91 0.91 D-5 (m) 0.91 0.91 0.91 0.91 0.91 0.91 D-6 (m) 0.91 0.910.91 0.91 0.91 0.91 D-7 (m) 0.91 0.91 0.91 0.91 0.91 0.91 L-1 (m) 0.610.61 0.61 0.61 0.61 0.61 L-2 (m) 0.30 0.30 0.30 0.30 0.30 0.30 L-3 (m)0.23 0.23 0.23 0.23 0.23 0.23 L-4 (m) 0 0 0 0 0 0 L-5 (m) 0 0 0 0 0 0L-6 (m) 0 0 0 0 0 0 L-7 (m) 0 0 0 0 0 0 Q (m) 5.0 5.0 4.0 4.0 4.0 5.0Combustion Air 1600 1600 1600 1600 1600 1600 (nm³/h) Combustion Air 753753 753 753 753 753 Preheat (K) Burner Nat. Gas 42 42 42 42 42 42(nm³/h) Feedstock 0.198 0.208 0.150 0.170 0.170 0.170 Injection OrificeDiameter (cm) No. Feedstock 3 3 3 3 3 3 Injection Orifices FeedstockRate 1.55 1.68 1.11 1.40 1.30 1.34 (104 × m³/s) Feedstock 448 443 453448 468 448 Temp. (K) K⁺ Concentration 274 236 734 780 485 2314 infeedstock (g/m³) Aux. HC 0.508 0.508 0.508 0.508 0.508 0.508 InjectionOrifice Diameter (cm) No. Aux. HC 3 3 3 3 3 3 Injection Orifices* Aux.HC Rate 30 32 22 27 50 26 (nm³/h)** Primary 400 400 400 400 400 400Combustion (%)*** Overall 25.8 23.7 34.6 28.3 28.9 29.5 Combustion(%)**** Quench Water 510 510 520 548 580 540 Rate (kg/h) *The feedstockand auxiliary hydrocarbon orifices were arranged in the same axial planein an alternating sequence around the periphery of the reactor. HC =hydrocarbon **nm³ refers to normal cubic meters, where “normal” refersto the gas volume corrected to 0° C. and 1 atm pressure ***Primarycombustion is defined as the percentage of oxygen added to the reactorcompared to the total amount of oxygen required to stoichiometricallyreact with the burner natural gas. ****Overall combustion is defined asthe percentage of oxygen added to the reactor compared to the totalamount of oxygen required to stoichiometrically react with all the fuelstreams added to the reactor.Characterization of Carbon Blacks

Various properties of carbon blacks produced in Example 1 were measuredas described elsewhere herein. The pH values shown were determined bydispersing 3 g of the material in 30 mL of water, boiling for 15minutes, cooling to room temperature, and measuring the pH of theaqueous phase with a pH probe (ASTM D1512-05). Spectronic 20 wasmeasured as per ASTM D1618-99. Na and K content were measured viainductively coupled plasma (ICP) analysis. As shown in Table 3, below,the carbon blacks exhibit low structure, high purity (low extractablesand low [K⁺]), neutral to mildly basic pH, and low WSP (e.g., they arehydrophobic).

TABLE 3 Example No. A B C D E C1 Iodine Number (mg/g) 47 33 123 73 69 95DBP (cc/100 g) 35 32 37 35 37 34 Nitrogen Surface 42 105 62 63 88 Area(m²/g) STSA Surface 41 31 104 61 63 88 Area (m²/g) Tint (%) 87 123 103105 110 Spectronic 20 (%) 99.5 75 98 98.5 100 Boiled pH 6.6 8.8 7.9 9.29.2 D-Mode (nm) 84 69 72 46 D-Stokes (nm)* 103 80 86 57 Na content(μg/g) 7.3 24.4 K content (μg/g) 434.1 1378 1221 927 3916 Ash content(wt %) 0.19 0.63 WSP (mJ/m²) 3.0 4.5 3.9 4.9 9.7 *Median Stokes diameterViscosity

The carbon blacks of Example A and a commercially available carbon black(Comparative Example C2) having the characteristics listed in Table 4,below, were used to prepare millbases with from 10 to 50 wt % carbonblack in PGMEA. The millbases also included a dispersant (Solsperse32500). The ratio between the dispersant and the carbon black was fixedat 0.2. The components were milled using a Skandex lab shaker for 4hours. The mean volume particle size of the pigments in the millbaseswere measured and found to be comparable to the aggregate size of basecarbon black. Solsperse 32500 is a polymeric dispersant commerciallyavailable from Noveon, and PGMEA is propylene glycol methyl etheracetate available from Sigma-Aldrich.

TABLE 4 Comparative Carbon Black Analytical Properties Example No. C2Iodine Number (mg/g) 71 DBP (cc/100 g) 46 Nitrogen Surface Area (m²/g)66 STSA Surface Area (m²/g) 66 Tint (%) 104 Spectronic 20 (%) 99 BoiledpH 7.6 D-Mode (nm) 77 D-Stokes (nm)* 87 Na content (μg/g) 191 K content(μg/g) 999 Ash content (wt %) 0.38 WSP (mJ/m²) 8.0 *Median Stokesdiameter

Viscosity measurements were conducted for millbase formulations usingcuvette geometry and a AR-G2 (TA Instruments) rheometer.

The millbase dispersions were Newtonian fluids. At 50% loading, thedispersion with Carbon Black C2 exhibitied non-Newtonian behavior,whereas the dispersion with Carbon Black A was Newtonian in the entirerange of carbon black concentrations studied. A key advantage of low DBPcarbon black is significantly lower viscosity, especially at highercarbon black loadings (see FIG. 3), which is beneficial for processing(for instance, by spin coating), and film properties (for example, filmsmoothness resulting from to better leveling off of a lower viscositycoating).

The foregoing description of preferred embodiments of the presentinvention has been presented for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed. Modifications and variationsare possible in light of the above teachings, or may be acquired frompractice of the invention. The embodiments were chosen and described inorder to explain the principles of the invention and its practicalapplication to enable one skilled in the art to utilize the invention invarious embodiments and with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto, and theirequivalents.

What is claimed is:
 1. A toner composition comprising at least a firstcarbon black, the first carbon black having an I₂ number from 30 mg/g to200 mg/g, a DBP from 20 cc/100 g to 39 cc/100 g, an M-ratio of from 1 toless than 1.24, and a concentration of Group IA and IIA elements, ingg/g, of at most y+(15*I₂ number), wherein y is
 250. 2. The tonercomposition of claim 1, wherein the first carbon black is characterizedby at least one of the following: the carbon black has a water spreadingpressure of at most 6 mJ/m², the carbon black has a pH from 6 to 10, thecarbon black has a tint obeying the equation tint=x+0.44*I₂ number,where x is from 45 to 90, or the carbon black has a tint of at least 80.3. The toner composition of claim 2, wherein the toner compositioncomprises a second carbon black.
 4. The toner composition of claim 3,wherein the second carbon black differs from the first carbon black inone or more of surface area, structure, primary particle size, alkaliand/or alkaline earth concentration, pH, Spectronic 20 value, tint, or asurface concentration of oxygen-containing groups.
 5. The tonercomposition of claim 3, wherein the second carbon black is an oxidizedcarbon black, a heat treated carbon black, or a modified carbon blackcomprising an attached organic group.
 6. The toner composition of claim1, wherein the first carbon black has an M-ratio of from 1 to less than1.22.
 7. A toner composition comprising at least a first carbon black,the first carbon black having an I₂ number from 30 mg/g to 200 mg/g, aDBP from 20 cc/100 g to 39 cc/100 g, and a concentration of Group IA andIIA elements, in μg/g, of at most y+(15*I₂ number), wherein y is
 250. 8.The toner composition of claim 7, wherein the first carbon black ischaracterized by at least one of the following: the carbon black has apH from 6 to 10, the carbon black has an M-ratio of from 1 to less than1.24, the carbon black has a water spreading pressure of at most 6mJ/m², the carbon black has a tint obeying the equation tint=x+0.44*I₂number, where x is from 45 to 90, or the carbon black has a tint of atleast
 80. 9. The toner composition of claim 8, wherein the tonercomposition comprises a second carbon black.
 10. The toner compositionof claim 9, wherein the second carbon black differs from the firstcarbon black in one or more of surface area, structure, primary particlesize, alkali and/or alkaline earth concentration, pH, Spectronic 20value, tint, or a surface concentration of oxygen-containing groups. 11.The toner composition of claim 9, wherein the second carbon black is anoxidized carbon black, a heat treated carbon black, or a modified carbonblack comprising an attached organic group.
 12. The toner composition ofclaim 8, wherein the first carbon black has an M-ratio of from 1 to lessthan 1.22.
 13. A toner composition comprising at least a first carbonblack, the first carbon black having an I₂ number from 30 mg/g to 200mg/g, a DBP from 20 cc/100 g to 39 cc/100 g, and an M-ratio of from 1 toless than 1.24.
 14. The toner composition of claim 13, wherein the firstcarbon black is characterized by at least one of the following: thecarbon black has a concentration of Group IA and IIA elements, in μg/g,of at most y+(15*I₂ number), wherein y is 250, the carbon black has a pHfrom 6 to 10, the carbon black has a water spreading pressure of at most6 mJ/m², the carbon black has a tint obeying the equation tint=x+0.44*I₂number, where x is from 45 to 90, or the carbon black has a tint of atleast
 80. 15. The toner composition of claim 14, wherein the tonercomposition comprises a second carbon black.
 16. The toner compositionof claim 15, wherein the second carbon black differs from the firstcarbon black in one or more of surface area, structure, primary particlesize, alkali and/or alkaline earth concentration, pH, Spectronic 20value, tint, or a surface concentration of oxygen-containing groups. 17.The toner composition of claim 16, wherein the second carbon black is anoxidized carbon black, a heat treated carbon black, or a modified carbonblack comprising an attached organic group.
 18. The toner composition ofclaim 13, wherein the first carbon black has a M-ratio of from 1 to lessthan 1.22.